V4L/DVB (8870): gspca: Fix dark room problem with sonixb.
When using the sonixb driver in a dark room and given that the autoexposure
algorithm starts with a setting most suitable for daylight, the picture
produced by the cam may actually be 100% black leading to a avg_lum value of 0,
so an avg_lum value of 0 does not always signal an exposure settings change
(which it normally does). This patch adds a check for the really black image
case and stops dropping all frames as invalid in this case.
Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/gspca/sonixb.c b/drivers/media/video/gspca/sonixb.c
index bde9ea9..64bc758 100644
--- a/drivers/media/video/gspca/sonixb.c
+++ b/drivers/media/video/gspca/sonixb.c
@@ -52,6 +52,7 @@
struct sd {
struct gspca_dev gspca_dev; /* !! must be the first item */
atomic_t avg_lum;
+ int prev_avg_lum;
unsigned char gain;
unsigned char exposure;
@@ -1022,10 +1023,19 @@
} else {
lum = data[i + 8] + (data[i + 9] << 8);
}
- if (lum == 0) {
+ /* When exposure changes midway a frame we
+ get a lum of 0 in this case drop 2 frames
+ as the frames directly after an exposure
+ change have an unstable image. Sometimes lum
+ *really* is 0 (cam used in low light with
+ low exposure setting), so do not drop frames
+ if the previous lum was 0 too. */
+ if (lum == 0 && sd->prev_avg_lum != 0) {
lum = -1;
sd->frames_to_drop = 2;
- }
+ sd->prev_avg_lum = 0;
+ } else
+ sd->prev_avg_lum = lum;
atomic_set(&sd->avg_lum, lum);
if (sd->frames_to_drop) {